For example, a pressurized water reactor (PWR) is a reactor that uses light water as a nuclear reactor coolant and a neutron moderator, makes high-temperature and high-pressure water that does not boil over the entire reactor internal, sends the high-temperature and high-pressure water to a steam generator to generate steam by heat exchange, and sends the steam to a turbine generator to generate electricity.
A reactor vessel that is used in such a pressurized water reactor is configured to include a reactor vessel main body and a reactor vessel lid that is mounted on an upper portion of the reactor vessel main body such that core internals can be inserted into the inside thereof, and is made such that the reactor vessel lid can be opened and closed to the reactor vessel main body. Then, in a case of detachably mounting the reactor vessel lid on the reactor vessel main body, a nut is fastened by passing a stud bolt through an outer peripheral flange of the reactor vessel lid, screwing and implanting the stud bolt into an outer peripheral flange of an upper portion of the reactor vessel main body, and screwing the nut while applying tension to the stud bolt.
As such a fastening and loosening device, there is a device described in Japanese Patent Application Publication No. 60-047072 (Patent Literature 1). In the device described in Patent Literature 1, four stud tensioning devices are connected to a single centralized control device and the centralized control device centrally controls the four stud tensioning devices.
In a nuclear power plant, in order to continue a safe and efficient enterprise, fuel exchange and check of a nuclear reactor and periodic inspection work of other peripheral equipment are carried out. Such works are indispensable for a safe operation in an electric power plant, whereas process observance and further process shortening are required under the economic demands. Mounting and dismounting work of the reactor vessel lid to the reactor vessel main body described above is carried out by a fastening and loosening device, and if the fastening and loosening device breaks down during work, it becomes difficult to perform opening of the nuclear reactor, thereby directly leading to subsequent process delay. Therefore, the fastening and loosening device needs to be able to reliably carry out the mounting and dismounting work of the reactor vessel lid and continue to complete the work in some way even when a fault has occurred in various equipments.
In the fastening and loosening device of the related art described above, since the single centralized control device centrally controls the four stud tensioning devices, in a case where a fault occurs in either of a control panel of the centralized control device or a control panel of each stud tensioning device, an operation of the entire device is stopped. At this time, since each stud tensioning device is controlled by the centralized control device, the stud tensioning devices cannot be operated independently. Then, since each stud tensioning device is centrally controlled by the centralized control device, a unique ID for identification is given thereto and replacement work of the control panel thereof or the like becomes cumbersome. As a result, recovery work at the time of a fault of the fastening and loosening device becomes large-scale and the mounting and dismounting work of the reactor vessel lid is performed over a long period of time.
The present invention is for solving the above-described problem and has an object of providing a fastening and loosening device that enables improvement in the reliability of the device.